AH: Remove a ND_TCHECK_SIZE() call

It was the last ND_TCHECK_*() call.
Remove the only trunc label.
diff --git a/print-ah.c b/print-ah.c
index b9364dc..a3d0554 100644
--- a/print-ah.c
+++ b/print-ah.c
@@ -46,7 +46,6 @@
 	ndo->ndo_protocol = "ah";
 	ah = (const struct ah *)bp;
 
-	ND_TCHECK_SIZE(ah);
 	nd_print_protocol_caps(ndo);
 /*
  * RFC4302
@@ -73,7 +72,4 @@
 	ND_PRINT("): ");
 
 	return ah_hdr_len;
-trunc:
-	nd_print_trunc(ndo);
-	return -1;
 }